The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

Govt foresaw pink batts safety issues

The Rudd government knew monitoring safety in the home insulation scheme would prove difficult before the program was even rolled out, an inquiry has heard.

The deputy director general of WA's Department of Premier David Smith has told a royal commission how the Commonwealth's ability to implement such a large program was a major issue that was never really addressed.

Mr Smith said the federal government was warned that the states and territories didn't have the regulatory framework to cope with the volume of insulation installations that would be driven by the program.

"Our existing regulatory regime (in WA) ... was not designed to deal with a program the scale of the HIP," he told the inquiry.

"It was an early and consistent message that was provided to me and conveyed to the Commonwealth."

Mr Smith said monitoring the standard of work being done under the program proved difficult.

"It was clearer by hindsight I guess but ... there were some pretty big warning bells," he said.